Tire non-uniformity relates to the symmetry (or lack of symmetry) relative to the tire's axis of rotation in certain quantifiable characteristics of a tire. Conventional tire building methods unfortunately have many opportunities for producing non-uniformities in tires. During rotation of the tires, non-uniformities present in the tire structure produce periodically-varying forces at the wheel axis. Tire non-uniformities are important when these force variations are transmitted as noticeable vibrations to the vehicle and vehicle occupants. These forces are transmitted through the suspension of the vehicle and may be felt in the seats and steering wheel of the vehicle or transmitted as noise in the passenger compartment. The amount of vibration transmitted to the vehicle occupants has been categorized as the “ride comfort” or “comfort” of the tires.
Tire uniformity characteristics, or attributes, are generally categorized as dimensional or geometric variations (radial run out (RRO) and lateral run out (LRO)), mass variance, and rolling force variations (radial force variation, lateral force variation and tangential force variation). Uniformity measurement machines often measure the above and other uniformity characteristics by measuring force at a number of points around a tire as the tire is rotated about its axis.
Once tire uniformity characteristics are identified, correction procedures may be able to account for some of the uniformities by adjustments to the manufacturing process. Some of the uniformities may be hard to correct during the manufacturing process and so additional correction procedures are needed to correct remaining non-uniformities of cured tires. A number of different techniques may be available, including but not limited to the addition and/or removal of material to a cured tire and/or deformation of a cured tire.
One known technique for correcting tire non-uniformities is the use of ablation along a bead portion of the tire. For instance, U.S. Patent Application Publication No. 2012/0095587, which is commonly assigned to the assignee of the present disclosure and which is incorporated by reference herein for all purposes, discloses the use of laser ablation along various tracks on the bead portion of a tire, such as along a bead seat zone, a lower flange zone, and an upper flange zone, of the tire. In particular, an ablation pattern for the tire beads is calculated to reduce the magnitude of one or more harmonics of at least one uniformity parameter. Material along the bead portion of the tire is then selectively removed using the calculated laser ablation pattern.
In some implementations, ablation of the bead of the tire can be performed using a plurality of direct address commands. The direct address commands can specify operating parameters for discrete ablation segments at specific azimuthal locations or “addresses” on the bead of the tire. More particularly, a desired ablation pattern can be broken down into a plurality of discrete ablation segments. These ablation segments represent small portions of the total ablation pattern that will be removed in incremental fashion by the ablation device. The direct address commands specify locations and other parameters for the plurality of discrete ablation segments to achieve a desired ablation pattern. U.S. Patent Application Publication No. 2014/0379116 which is commonly assigned to the assignee of the present disclosure and which is incorporated by reference herein for all purposes, discloses the use of direct address commands in selectively removing tire material from the bead portions of a tire.